docs/globals.txt

   1 globals.txt
   2
   3 Globals are evil. The original MediaWiki code relied on globals for processing
   4 context far too often. MediaWiki development since then has been a story of
   5 slowly moving context out of global variables and into objects. Storing
   6 processing context in object member variables allows those objects to be reused
   7 in a much more flexible way. Consider the elegance of:
   8
   9     # Generate the article HTML as if viewed by a web request
  10     $article = new Article( Title::newFromText( $t ) );
  11     $article->view();
  12
  13 versus
  14
  15     # Save current globals
  16     $oldTitle = $wgTitle;
  17     $oldArticle = $wgArticle;
  18
  19     # Generate the HTML
  20     $wgTitle = Title::newFromText( $t );
  21     $wgArticle = new Article;
  22     $wgArticle->view();
  23
  24     # Restore globals
  25     $wgTitle = $oldTitle
  26     $wgArticle = $oldArticle
  27
  28 Some of the current MediaWiki developers have an idle fantasy that some day,
  29 globals will be eliminated from MediaWiki entirely, replaced by an application
  30 object which would be passed to constructors. Whether that would be an
  31 efficient, convenient solution remains to be seen, but certainly PHP 5 makes
  32 such object-oriented programming models easier than they were in previous
  33 versions.
  34
  35 For the time being though, MediaWiki programmers will have to work in an
  36 environment with some global context. At the time of writing, 418 globals were
  37 initialised on startup by MediaWiki. 304 of these were configuration settings,
  38 which are documented in DefaultSettings.php. There is no comprehensive
  39 documentation for the remaining 114 globals, however some of the most important
  40 ones are listed below. They are typically initialised either in index.php or in
  41 Setup.php.
  42
  43 $wgTitle
  44         Title object created from the request URL.
  45
  46 $wgOut
  47         OutputPage object for HTTP response.
  48
  49 $wgUser
  50         User object for the user associated with the current request.
  51
  52 $wgLang
  53         Language object selected by user preferences.
  54
  55 $wgContLang
  56         Language object associated with the wiki being viewed.
  57
  58 $wgParser
  59         Parser object. Parser extensions register their hooks here.
  60
  61 $wgRequest
  62         WebRequest object, to get request data
  63
  64 $wgMemc, $messageMemc
  65         Object caches